With regard to break-in of factory barrels, I can offer this observation: In three brand-new rifles that I broke in over the last 3 years, (700, M-77 Mk II, M-70) I ran dry patches through each and found... shavings! No kidding! I was esp. shocked to find fresh stainless steel shavings down the bore of the Sendero! You can do what you want afterwards, but ALWAYS clean the bore thoroughly before that first shot out of a production rifle. You might also want to strip the action and carfully wipe the lugs, too. I just can't believe that steel shavings grinding down your bore with the force of your first group can be very good for your future accuracy!